The present invention relates to a vacuum treatment system with at least one vacuum treatment chamber, wherein a first part of the system is connected with an electrical system reference potentialxe2x80x94by convention ground potential; in the vacuum chamber a further part is provided to which is applied an electric potential varying by at least xc2x112 V from the system reference potential, and wherein at this further part at least one sensor and/or at least one adjusting element is disposed, further with an electronics unit which is operatively connected at the input and/output side with the sensor and/or adjusting element.
Such a prior known vacuum treatment system is depicted schematically in FIG. 1 as an example with a path of plasma discharge and will be discussed in conjunction with this Figure. In the vacuum chamber 1 a plasma discharge path is provided in this example between electrodes 3a and 3b. The discharge path denoted by 3 is operated electrically by a supply unit 5, with this being either DC, pulsed DC, with AC or with AC and superimposed DC, wherein the AC signal frequency can be in the Hz up to the high frequency, for example even in the microwave range.
For the purpose of explanation, in FIG. 1 the electrical supply leads to the discharge path 3 from the chamber 1 are shown as being electrically insulated. Different ways exist of superimposing the system reference potential, by convention ground potential xcfx860. This is schematically shown by the option selection switch 7. It is conventional, for example, to put the housing 1 as well as one of the electrodes 3a, 3b at ground. In the vacuum chamber 1 a further part 9 is depicted, for example a substrate support, an instrument support, a further electrode etc., wherein this part 9, shown separately for the purpose of the explanation, can also be one of the electrodes 3a, 3b. This part 9 is now not at potential xcfx860. This is shown with the unit 4 according to an impedance and/or source equivalent circuit diagram.
The present invention builds on problems in connection with part 9 in the chamber 1 to which (part) the system reference potential xcfx860 is not applied. It is at any electrical potential xcfx869 varying decisively, i.e. by at least xc2x112 V, from xcfx860, i.e. it is at DC potential, AC potential, at superimposed AC and DC potential, at a pulsed DC potential, wherein in terms of frequency the AC potential can be launched up into the high-frequency range or even into the microwave range. If, for example, part 9 is a substrate support, it can, if mounted electrically insulated, be operated with respect to xcfx860, on self-bias potential of the discharge. If part 9 is one of the electrodes 3a, 3b in the case of plasma generation, it is at high HF potential with respect to xcfx860.
As shown further in FIG. 1, it is frequently necessary to carry out measurements or adjusting intervention at said part 9, not operated at system reference potential xcfx860, as is schematically shown on unit 11, by means of at least one sensor and/or at least one adjusting element. Adjusting signals or sensor output signals are transmitted from an electronics unit 13 to the unit 11 or received by the latter. As shown in FIG. 1, it is conventional to apply to such an electronics unit 13 the system reference potential xcfx860. Such an electronics unit is often
a digital, programmable unit with storage means for the operating programs, therein preferably comprising
at least one programmable digital logic package and/or
a digital computing unit,
it preferably comprises a microprocessor and/or a microcomputer with associated storage means for operating programs.
The reason for the reference potential placement comprises that for example with HF operation of the discharge path, simple protective measures are possible, as shown schematically at 15, for example by means of shielding also placed at xcfx860. Furthermore, the signal communication between unit 13 and a unit 17 supervisory to it, such as for example a supervisory computer, is especially simple. The communication interface 19 comprises as reference potential the system reference potential xcfx860 which, as stated, is by convention ground potential. Under the assumption of the communication connection between unit 11 and unit 13, which is schematically shown by 21 in FIG. 1, also, if appropriate, feed signals for unit 11 from an external feed device, the supplied voltages to unit 11 are reduced through suitable electronic means to the measuring or total adjusting range of by convention a few volts. For this purpose are used, for example, voltage dividers, as described in U.S. Pat. No. 5,270,637, and/or suitable rectifiers and filter elements, as shown in U.S. Pat. No. 5,144,231.
This prior known configuration entails problems:
Measuring and adjusting signals from respectively to the unit 11 must be isolated from often large xe2x80x9cCommon Modexe2x80x9d signals, namely from the signal, already mentioned, between part 9, xcfx860 and xcfx869. This entails expenditures in particular if part 9 is at HF potential, in particular high HF potential, or at a potential with high spectral components of higher frequencies, such as occur during pulse operation, interference spark formation, switch-on processes etc. But even if the part 9 were at an ideal DC potential with respect to xcfx860, the problem remains that on unit 11 relatively small measuring or adjusting signals with respect to a large xe2x80x9cCommon Modexe2x80x9d signal must be processed which strongly limits the accuracy or resolution of said measuring or adjusting signals. If part 9 is operated for example at HF potential, for each individual measuring or control line from, respectively to, the unit 11 an HF filter must be providedxe2x80x94with, depending on the expenditure, restricted effectxe2x80x94as well as for each additional signal, such as for example for feed signals to unit 11 in order to ensure an optimal HF uncoupling with respect to the electronic unit 13. This entails considerable expenditures. In addition, in particular measuring and control signal lines to unit 11 must be efficiently shielded, especially if the, by convention, high-ohmic and sensitive inputs of unit 13 are taken into consideration. In principle, expensive precautionary measures for protecting the electronics must be provided.
It is the task of the present invention to develop a vacuum treatment system of the discussed type such that a substantial simplification of the signal processing with the electronic unit 13 results, further a more accurate measurement signal evaluation or a more precise adjusting element variation and which is significantly more cost effective. This is attained thereby that the electronics unit, differing from the prior known technique described in conjunction with FIG. 1, is operated at a further reference potential which further reference potential is equal to the potential of the further part 9.
The potential placement is especially highly effective with low expenditure where the operation of the vacuum treatment system leads to the occurrence of, to some extent stochastic, high-frequency signal components. A vacuum treatment system in which such processes occur frequently is in particular a system in which a discharge path is used.
In such a system said further part 9 forms preferably one of the discharge electrodes or is a part exposed to the discharge operated at a floating potential and thus, for example assumes the self-bias potential of the discharge or which is operated tied in potential.
In a further preferred embodiment, therein in particular in said system with discharge path, said at least one sensor is a temperature sensor, the adjusting element is a heating and/or cooling device, therein preferably a multizone heating or cooling device, wherein further, preferred in this case, the further part 9 is formed by a workpiece support. A temperature control can therein be realized or, preferably, a temperature regulation. The sensor or a multiplicity of provided sensors acquires the regulation parameters, temperature or temperature distribution. At the electronics unit, at the potential of part 9, either the regulating parameter measuring signal is amplified and supplied at the output side on a higher level insensitive to higher interference variables to a supervisory unit, at which a SET/INSTANTANEOUS value comparison takes place and at which, if appropriate, also the regulator is realized with the desired characteristic. The fed-back signal is supplied from the supervisory unit to said electronics unit on part 9, which outputs the temperature or temperature distribution actuator signal to the temperature adjusting element(s). Otherwise, the electronics unit preferably forms directly the SET/INSTANTANEOUS value comparison and the desired regulator characteristic.
In this approach temperature accuracies of at least xc2x15xc2x0 C. in total adjusting ranges of a few 100xc2x0 C. full scale can readily be achieved, preferably of at least xc2x12xc2x0 C. or even of at least xc2x11xc2x0 C. Such a temperature control or guidance accuracy did present large problems in known processes according to FIG. 1.
Such a temperature guidance is in particular highly desired if said part 9 is a workpiece support in the system or if part 9 is a target configuration of the system.
In a further preferred embodiment, said part 9 forms a workpiece holding fixture. The sensor verifies the presence or absence of a workpiece on the holding fixture. If the workpiece holding fixture forming said part 9 comprises a holding element acting electrostatically or by underpressure onto the workpiece, said sensor or a further sensor is preferably provided for verifying the workpiece mounting, and preferably a feedback from the sensor via the electronics unit onto said mounting is carried out.
Consequently it is possible to verify the adhesion condition or the mounting of the workpieces in the chamber and, if necessary, to readjust or reregulate them.
In a further preferred embodiment of the system said further part 9 is provided directly in the region of a gas inlet into the vacuum chamber and the sensor is developed as a gas flow sensor. The electronics unit acts at the output side onto an adjusting valve configuration in a gas guidance for the gas inlet.
Alternatively, in the last described process, said part 9 is provided in the immediate region of a workpiece. In this way it is possible in any event to carry out a precise gas inlet control or regulation directly at the location of the critical event which permits without delay the fast and precise response to instantaneous operation conditions variation from the set operation.
As already indicated on a further preferred embodiment the further part 9 is provided on a target configuration, where the sensor measures or detects the temperature of the target and/or its condition. In spite of difficult electrical situations in the environment of the target (through transients, for example triggered through interference sparking), through the process according to the invention it is possible, to detect with high accuracy target temperatures or generally target conditions such as for example its erosion mass and to carry out control or regulatory interventions via the electronics unit.
Said electronics unit operated at the potential of part 9 can therein be provided quite outside of the vacuum chamber; but at least its input stage for the sensor or output stage for the adjusting element are preferably disposed in the immediate region of said sensors or adjusting elements and thus in the vacuum chamber.
In a further preferred embodiment of the system according to the invention the further part 9 is at an AC and/or DC potential with respect to the system reference potential or is disposed such that it is electrically insulated from the system reference potential. AC comprises therein in particular the HF range, but can extend up into the microwave range. The further part is preferably a substrate or workpiece support. In particular in that case the provision of sensors and/or adjusting elements, such as for example for the described temperature setting or regulation, is often desired.
If the further part is at an HF potential with respect to the system reference potential, also, for example for bias operation relative to a plasma, thus preferably in a frequency range of 100 kHz to 100 MHz, therein preferably between 5 MHz and 50 MHz, therein preferably between 5 MHz and 50 MHz, in particular preferred at the industrial frequency of approximately 13.56 MHz. The potential difference xcfx860xe2x88x92xcfx869, is further preferably as follows:
|xc2x112|Vxe2x89xa6|xcfx860xe2x88x92xcfx869|xe2x89xa6|xc2x12000|V,
preferably
|xc2x125|Vxe2x89xa6|xcfx860xe2x88x92xcfx869|xe2x89xa6|xc2x1500|V.
Peak-to-peak voltage Vpp on said part 9 and with respect to system reference potential at AC, in particular HF operation, are preferably in the range
25Vxe2x89xa6Vppxe2x89xa6200V,
therein preferably:
50Vxe2x89xa6Vppxe2x89xa6500V.
In a further preferred embodiment said electronics unit comprises at least one digital, preferably programmable unit, preferably at least one programmable digital logic package and/or at least one digital computing unit, preferably at least one microprocessor and/or microcomputer. If required, at the electronics unit are preferably provided storage means for operating programs.
Further preferred, the electronics unit is mechanically disposed directly on said further part 9. In particular in the case the further part 9 is at an HF potential, said electronics unit is preferably encompassed by a Faraday cage which is preferably at the potential of part 9. It is further preferably proposed that the connections from and/or to the electronics unit are carried at least to some extent over galvanic isolation sites and/or over HF filter configurations. Such filter configurations are therein preferably encompassed by a Faraday cage configuration placed at the system reference potential.
In a preferred embodiment said electronics unit communicates with a supervisory adjusting and/or monitoring unit, for example a host computer disposed outside of the vacuum chamber. Signal connections between the electronics unit and the supervisory unit preferably take place via a galvanic isolation site such as over ratio transformers, preferably via light waveguides.